Over the past 20 years, revolutionary changes have occurred in the method and apparatus used for harvesting and curing tobacco. These changes have stemmed largely from the development of bulk curing techniques for curing tobacco.
Essentially the bulk curing method involves packing large quantities of tobacco leaves together in a face to face relationship in a heated, forced air recirculation kiln or barn. The leaves are placed so that their surfaces lie in a vertical plane and the heated air is forced upwards through the bulk pack so as to cure all of the tobacco within. An example of bulk curing methods is disclosed in Hassler, Canadian Patent No. 751,105.
Various methods and means were developed for making bulk packs and for simplifying and mechanizing tobacco harvesting and handling operations. Initially bulk packing of the tobacco leaves was accomplished by piercing the leaves onto a rack of tynes. An example of such a tobacco rack is disclosed in U.S. Pat. No. 3,143,370 to T. J. Danford et al. Harvesters were adapted to this type of rack, for example, see Long U.S. Pat. No. 3,834,137. Loading and unloading mechanisms for bulk packed tobacco were developed, see Green et al, U.S. Pat. No. 4,016,985 as well as trailers for transporting the bulk packed tobacco, see Long U.S. Pat. No. 3,095,230.
One of the important steps towards the simplification and mechanization of tobacco harvesting and curing was the development of methods of bulk packing and curing tobacco in large bins. An example of a tobacco container or bin and the related method of curing is disclosed in Long U.S. Pat. No. 3,935,959. In essence the concept is that the tobacco leaves are distributed into a bin with the leaf faces horizontal but otherwise randomly oriented until the bin is filled. Then the bin is closed and the tobacco leaves are pierced through vertically by retaining rods. The bin is then turned over on its side so that the leaf faces are vertical. The formation of the bulk pack is maintained by the now horizontal retaining rods. The bin in this position with other bins, is then placed in a forced air recirculation kiln. The bottom and top of the bin are usually perforated or open to permit the circulation of curing air through the bulk packed tobacco.
The development of containers for bulk curing led to the development of harvesters adapted to discharge the tobacco leaves directly into the bins or containers. When a bin was filled it could be replaced by another bin and taken to a curing kiln. Examples of harvesters of this type are found in Long U.S. Pat. No. 3,946,542 and Johnson, U.S. Pat. No. 3,885,376. However, as pointed out in Suggs, U.S. Pat. No. 4,047,365 a harvester discharge will tend to form a cone shaped pile in a container unless some leaf distribution means is provided. The cone shaped pile is unacceptable for the curing step because non-uniform distribution tends to permit air leakage through the less dense parts of the bulk pack and to deprive the more densely packed portions. Suggs U.S. Pat. No. 4,047,365, and Johnson U.S. Pat. No. 3,885,376 both provide mechanical means for obtaining an even distribution of leaves.
Another problem is discharging leaves from a harvester, where the discharge means includes a conveyor belt, is that sometimes leaves tend to stick to the belt and are not discharged properly. This problem was dealt with by using scavaging rollers to scrape under the discharge end of the conveyor belt in Mitchell, U.S. Pat. No. 4,037,391.